# std::iter_swap(std::reverse_iterator)

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< cpp‎ | iterator‎ | reverse iterator

template< std::indirectly_swappable<Iter> Iter2 > friend constexpr void iter_swap( const reverse_iterator& x, const std::reverse_iterator<Iter2>& y ) noexcept(/* see below */); |  | (since C++20)

Swaps the objects pointed to by two adjusted underlying iterators.

Equivalent to auto tmp_x = x.base();
auto tmp_y = y.base();
ranges::iter_swap(--tmp_x, --tmp_y);.

This function template is not visible to ordinary unqualified or qualified lookup, and can only be found by argument-dependent lookup when std::reverse_iterator<Iter> is an associated class of the arguments.

### Parameters

x, y | - | reverse iterators to the elements to swap

### Complexity

Constant.

### Exceptions

`noexcept` specification:
noexcept(

std::is_nothrow_copy_constructible_v<Iter> &&
std::is_nothrow_copy_constructible_v<Iter2> &&
noexcept(ranges::iter_swap(--std::declval<Iter&>(), --std::declval<Iter2&>()))

)

### Example

Run this code

    #include <iostream>
    #include <iterator>
    #include <list>
    #include <vector>

    int main()
    {
        std::vector v{1, 2, 3};
        std::list l{4, 5, 6};

        std::reverse_iterator<std::vector<int>::iterator> r1{v.rbegin()};
        std::reverse_iterator<std::list<int>::iterator> r2{l.rbegin()};

        std::cout << *r1 << ' ' << *r2 << '\n';

        iter_swap(r1, r2); // ADL

        std::cout << *r1 << ' ' << *r2 << '\n';
    }

Output:

    3 6
    6 3

### See also

swap | swaps the values of two objects (function template)
swap_ranges | swaps two ranges of elements (function template)
iter_swap | swaps the elements pointed to by two iterators (function template)
iter_swap (C++20) | swaps the values referenced by two dereferenceable objects (customization point object)
iter_swap (C++20) | swaps the objects pointed to by two underlying iterators (function template)

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